Interaction between the human embryo and the lining of the uterus (the endometrium) is critical when it comes to implantation, development of the placenta, and ultimately achieving a healthy pregnancy and live birth. This interaction between the embryo and endometrium is a complex and incompletely understood process.

The timing of this interaction during the window of implantation, leading to embryo and endometrial synchrony, has only recently been noted to be a critical factor. This is impacted by IVF laboratory conditions and embryonic growth as well as medical management of the ovarian stimulation and endometrial preparation. Work in this area seeks to better characterize the physiology and pathophysiology involved in this process in order to maximize the chance of a single, healthy live birth per embryo transfer.